Process for cracking petroleum hydrocarbons



Aprifl iz, 1932. A. 51D. DAVID 1,854,115

PROCESS FOR CRACKING PETROLEUM HYDROCARBONS Filed Feb. 12, 1925 I fl ubre y-D.pavic/ Patented Apr. 12, 1932 UNITED STATES" PATENT err-tics.

AUBREY ID. DAVID, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE UNIVERSAL OIL PROD- UCTS COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF SOUTH DAKOTA PROCESS FOR onncxme PETROLEUM nvnnoonanons Application filed February 12, 1923. Serial No. 618,485. I

This invention relates to improvements in a process and apparatus for the pressure distillation and cracking of petroleum hydrocarbons, and'refers more particularly to the converting of relatively high boiling point oils to oils of a low boiling point having the characteristics of gasoline. I Among the objects of the invention are to provide a process in which the heat of the reflux is utilized as a preheating agent and the cooled reflux condensate recycled through the dephlegmating stage and there used as a refluxing medium to control the character of the vapors permitted to pass over for condensation. i

The single figure is a diagrammatic side elevational view of the apparatus.

Referring to the drawing at 1 is shown a furnace in which are mounted the heatingtubes 2. The. tubes are connected through a transfer line'3 to an expansion chamber 4 which is equipped with try-cocks 5 for'ascertainin the liquid level, and drawofli' lines 6 contro led by valves 7 for removing the unvaporized oil and residual substances from the chamber. The expansion chamber is connected by a vapor. line 8 regulated by a valve 9 to dephlegmating column 10 in which the oil is subjected to a refluxing action. From the top of the dephlegmator a pipe 11 leads to a water condenser 12, the discharge end of which is connected by a line 13 to a receiving tank 14. At 15 is'shown the reflux cooling coil mounted in the tank 16. A coil 15 is connected to the reflux leg 10a by means of a pi'pe'17 controlled by a valve 18, The discharge end of the cooling coil 15 is connected 1 to the suction side of the recycling pump 19 by means of apipe 20 regulated by the valve 21. The oil discharged from the pump 19 is directed through the line 22 regulated by a valve 23 back into the'top of the dephlegmator where may be introduced by means of a spray pipe, not shown, in order to distribute the recycled material -more thoroughly throughout the column.

,Referring now to the method in which the oil is treated, a charging stock procured from any convenient source not shown, is introduced throughthe line 24 regulated by the the remainder *3 and is collected in a substantial body in the expansion chamber 4. In the expansion chamber the vapors are separated from the oil body and pass off through the vapor line 8 tothe' dephlegmator where they are subjected to a refluxing action.

The unvaporized liquid portion remaining in the expansion chamber, is drawn ofl' either intermittently or continuously through the drawofl' lines 6. The vapors after being subjected to a refluxing action in the dephlegmator 10 pass over and are condensed at 12 and are'finally collected as liquid distillate in the receiving tank14. The receiving tank is equipped with a pressure relief pipe 28, a pressure gauge 29,- a liquid level gauge 30 and a liquid drawofi valve 31.

Pressures on the. system may be regulated by valves interposed in the connecting lines between the separate stages ora uniform pressure maintained by manipulation of the relief valve 28 on the receiving tank.

The reflux condensate separated during the dephlegmation of the vapors in the refluxing column, collects in the lower leg of the dephlegmator and may be recycled back to the heating coils through the line 32 controlled by the valve 33, or by closing valve 33 and opening the valve 18 this'hot reflux may be circulated through the cooling coil 15' and recycled back into the top of the dephlegmator through the line 22, it being of course', obvious that part of the reflux condensate can be recycled back to the heating coil and coil. v

In operating in this manner, an accurate regulation of the temperatureof the vapors permitted to pass over from the top of the as passed through the cooling dephlegmator to the final condensing stage, may be assured.

A temperature registering device such as a thermostat may be inserted in the top of the dephlegmator to ascertain the temperature of the vapors at this point.

The recycled reflux is well known as a relatively refractory oil, and by cooling in this manner makes an admirable refluxing medium as it will be but little afi'ected'by the temperatures maintained in the top of the column.

Where a charging stock or oil readily susceptible to temperatures maintained in the dephlegmating stage, is introduced and utilized as a refluxing medium. there are often objectionable fractions carried over, either mechanically or due to the conversion of this oil with the dephlegmated vapors. These light or what are commonly termed as wild cat fractions are objectionable as they produce a distillate which is not uniformin character. In cracking an oil in this type of apparatus, there is a considerable quantity 0 reflux produced. 'Oftentimes during operation, the quantity is in excess of the amount which it is advisable to recycle,'as the oil is of a relatively refractory nature and unless excessive temperatures are resorted to in the heating stage, adequate conversion is not produced.

By utilizing a portion of this oil as a refluxing medium and recycling it back to the top of the dephlegmator in this manner, not only a better control of the apparatus is had, but also a more uniform pressure distillate is produced in the receiving tank.

By treating gas oil of approximately 32 Baum to temperatures ranging from 700 to 900 F., and maintaining pressures from 50 to 300 pounds upon the oil during treatment, a high quality distillate of from 30% to 50% of the charging stock is produced having a gravity of from 48 to 52 Baum.

I claim as my invention:

1. An improvement in an oil cracln'ng process in which the oil is supplied to a heating coil wherein it is raised to a cracking temperature, thence delivered to an enlarged zone wherein substantial vaporization occurs, the vapors being delivered to a reflux condenser in which the insuificiently cracked fractions are condensed forming reflux condensate, comprising the continuous circulation of reflux condensate separated from the vapors in said reflux condenser through a closed ring, including said reflux condenser and a zone outside of said reflux condenser, through which the reflux condensate circulating in the ring passes in heat interchange relation, but out of contact, with incoming cool charging oil being supplied to the heating coil.

2. An improvement in an oil cracking proces in which the oil is supplied to a heating coil wherein it is raised to a cracking temperature, thence delivered to an enlarged zone wherein substantial vaporization occurs, the vapors being delivered to a reflux condenser in which the insufficiently cracked which the reflux condensate flows in heat interchange relationship with incoming charging oil, and supplying such removed portion of the reflux condensate to said heating coil with the incoming chargin oil.

AUBREY D. D VID. 

